BULLETIN FLORIDA MUSEUM NATURAL HISTORY 38(1)


 Low recapture rates in amphibian studies have led some authors to conclude
that mortality rates are very high from one year to the next (e.g. Given 1988).
Although G. carolinensis possesses noxious skin secretions (Garton and
Mushinsky 1979), many vertebrates and invertebrates probably prey on this
abundant resource. This species also seems particularly sensitive to desiccation
(Anderson 1954; Wygoda 1984). Mortality at the pond or in refugia certainly
occurs, but whether it accounts for the low multi-year recapture percentages cannot
be ascertained.

 Seasonal Activity.-Some G. carolinensis were active throughout the year at
Breezeway Pond, although adult activity was greatly reduced from October through
April. Juveniles were active in all months, especially in the autumn, presumably as
they dispersed. Peak population activity occurred from June through September as
adults moved toward and away from Breezeway Pond. This period is similar to
that reported elsewhere for this species (Wright 1932), although the breeding
season extends from April through September in the southern parts of the range
(Anderson 1954; Mount 1975; Dundee and Rossman 1989). April and May were
very dry months at Breezeway Pond from 1986 through 1990, perhaps accounting
for the lack of activity in these months.
 Activity of Gastrophryne is definitely influenced by rainfall (Deckert 1914;
Wright 1932; Freiburg 1951; Anderson 1954; Fitch 1954). Heavy rains from June
through September stimulated adult animals to move to breeding sites. Movement
occurred during the rainy period, and there was no evidence of a lag effect. The
amount of rain needed to trigger movement varied with previous weather
conditions. If rainfall was regular, high amounts of rain were required to stimulate
movement. However, during droughts, rainfall of as little as 2 mm stimulated
substantial numbers of toads to move toward or away from the pond.
 Although small amounts of rainfall can trigger movements to breeding ponds
by amphibians (e.g. Semlitsch 1985; Dodd and Charest 1988; Sexton et al. 1990),
most G. carolinensis move to ponds only after heavy rains, except after prolonged
periods without rain. Rainfall in April and May was never greater than 20 mm on
any one day from 1986 through 1990 at Breezeway Pond. Amounts were generally
1-10 mm. Few G. carolinensis moved during these months, although eastern
narrow-mouthed toads breed in April and May elsewhere in Florida (Carr 1940;
Duellman and Schwartz 1958) and nearby southern Georgia (Wright 1932).
Presumably, movement and reproductive behavior would have commenced in April
or May at Breezeway Pond if heavy rainfall had occurred.
 Two peaks of immigration by unmarked animals of both sexes were evident
annually from 1986 through 1989. The first occurred in June, and the second
occurred in August. Two hypotheses are possible. The first is that two temporally
segregated groups of toads breed in Breezeway Pond. Alternatively, the August
pulse of unmarked animals represents toads that bred elsewhere and were moving